Pressure sensitive adhesives (PSA) are well known and are used in many industrial, consumer and medical applications. Pressure sensitive adhesives are formulations typically comprising an elastomeric polymer, a tackifier, and optionally an oil or other additives. These adhesives remain permanently tacky and adhere instantaneously to a wide variety of surfaces with the application of a small amount of pressure. Pressure sensitive adhesives are generally used in the form of a coating on a backing, such as in adhesive bandages, wound dressings, transdermal delivery devices, tapes, stencils, wall paper, envelopes, stamps, and floor tiles.
For many applications, it is desirable to be able to remove the adhesive from the surface without significant force, so that the surface, for example, newly healed skin, is not damaged. For this reason, switchable adhesives, which undergo a reduction in peel strength with a change in conditions, have been developed. Switchable adhesives that exhibit a reduction in peel strength upon contact with water or exposure to UV radiation are known. Particularly useful for some adhesive applications are temperature switchable adhesives, which undergo a reduction in peel strength with a temperature change. For example, Stewart (U.S. Pat. Nos. 5,156,911 and 5,387,450) describes a temperature switchable adhesive composition comprising a side chain crystallizable polymer. Additionally, Schmitt et al. (U.S. Pat. No. 5,412,035) describes pressure sensitive adhesive compositions containing a crystalline polymeric additive that lose adhesive strength upon heating. The crystalline polymeric additive is preferably a side chain crystallizable polymer having a weight average molecular weight of less than 25,000. However, new approaches to preparing temperature switchable adhesives are needed to meet the requirements for many different applications.
Therefore, the need exists for new temperature switchable adhesives for which the temperature switching properties may be readily adjusted to meet the requirements for many different applications by readily changing the tackifier, elastomer, and oil used in the formulation, according to standard principles of adhesive formulation.